1. Field of the Invention
The present invention relates to the field of baseband computer networks. Specifically, the present invention relates to a method and apparatus utilized by a dual speed 10/100 Mb/s physical layer device. The dual speed device provides support for transmitting waveshape information compatible with the Institute of Electrical and Electronic Engineers (IEEE) 802.3 Clause 14, 10 million bits per second (10 Mb/s) Physical Layer specification, i.e., IEEE 802.3 Standard 10BASE-T Ethernet, over a service interface in the physical layer.
Although not specified in IEEE 802.3, the interface can also be utilized in the implementation of 100 million bits per second (100 Mb/s) Local Area Network (LAN) physical layer devices compatible with the Physical Layer specifications defined in the IEEE 802.3u Supplement (excepting Clause 23 and 26), i.e., IEEE 802.3 Standard 100BASE-TX Ethernet.
2. Description of the Related Art
Overview of 10 MbAs and 100 Mb/s Baseband Networks
To better appreciate and understand the present invention, a brief overview of relevant aspects of 10 Mb/s and 100 Mb/s baseband local area networks follows. The operation of a Local Area Network (LAN) is often described in terms of the International Standards Organization (ISO) seven-layer Open Systems Interconnection (OSI) abstract reference model. Referring to FIG. 1, the relationship between the seven-layer OSI reference model 100 and the IEEE 802.3 architectural layers for 1 Mb/s to 20 Mb/s operation model 110 and 100 Mb/s operation model 115 are shown.
10BASE-T is an IEEE standard 802.3 and ISO/IEC standard 8802-3 Physical Layer specification for 10 Mb/s Ethernet LANs. 100BASE-T is an IEEE 802.3 standard supplement (802.3u ) Physical Layer specification for 100 Mb/s Ethernet LANs. The 802.3u standard extends the speed of the 802.3 Media Access Controller (MAC) to 100 Mb/s while utilizing the existing MAC service interface 102 of MAC 120. MAC service interface 102 is connected through a Reconciliation sublayer 103 and a Media Independent Interface (MII) 130 to a Physical Layer Device (PHY) sublayer 104. The MII is the IEEE 802.3 standard specification for a dual speed 10/100 Mb/s service interface in the Physical Layer 10, although implementation of the MII is optional.
The PHY sublayer 104 may be specified for operation at data rates of either 10 Mb/s or 100 Mb/s. The specifics of a 10 Mb/s PHY sublayer connected to an MII are not explicitly defined by the 802.3 standard, but inferred to match the overall system performance objectives of the MAC 120, PLS 121, AUI 113, PMA 114, and MDI 111 architecture at 10 Mb/s.
Multiple PHY sublayers have been specified in IEEE standard supplement 802.3u (and later supplements) for operation at 100 Mb/s. The current list of 100 Mb/s PHY sublayer specifications includes 100BASE-T4, 100BASE-T2 and 100BASE-X.
100BASE-T4 specifies the use of four pairs of category 3, 4 or 5 Unshielded Twisted Pair (UTP) wire and supports only half duplex operation. 100BASE-T2 specifies the use of two pairs of category 3,4, or 5 UTP wire and supports full duplex operation. 100BASE-X supports two embodiments, both of which support full duplex operation: 100BASE-TX and 100BASE-FX. 100BASE-TX specifies the use of 2 pairs of category 5 UTP or shielded twisted pair (STP) wire. 100BASE-FX specifies the use of 2 optical fibers. Generally, the term 100BASE-X is used when referring to characteristics common to both 100BASE-TX and 100BASE-FX.
100BASE-X is an IEEE standard 802.3 Physical Layer specification for 100 Mb/s LANs that uses the FDDI signaling standards. 100BASE-X encompasses 100BASE-TX (which references ANSI X3T9.5 TP-PMD/312, Revision 2.2, FDDI Twisted Pair Physical Medium Dependent (PMD) sublayer), and 100BASE-FX (which references ISO 9314-3, 1990, Fiber Distributed Data Interface (FDDI)--Part 3: Token Ring PMD sublayer).
As described in clause 28 of IEEE standard 802.3u, Auto-Negotiation is an optional function that allows a network device, such as a workstation, switch or repeater, coupled to a point-to-point link segment, to advertise the modes of operation of which it is capable to a network device at the other end of the point-to-point link segment and detect corresponding operational modes that the other network device may be advertising. Auto-Negotiation provides the capability for future technology upgrades and can be modified to advertise such modes of operation as types of physical layer devices available, full -duplex communication, and flow control. Auto-Negotiation further provides, through the use of the Parallel Detect Algorithm, the ability to detect and interoperate with legacy, non-Auto-Negotiation, half duplex, 10BASE-T, 100BASE-TX and 100BASE-T4 based nodes where applicable. Auto-Negotiation is designed for LANs implemented using unshielded twisted pair (UTP) copper wire and the well known, ISO/IEC 8802, eight-pin modular jack (RJ-45 connector). The signaling mechanism used in Auto-Negotiation is backwards compatible with the installed base of 10BASE-T baseband computer networks as defined in IEEE 802.3 Clause 14.
10BASE-T operation employs a discontinuous signaling method over the transmission medium. When data is not being sent over the medium, the voltage on the medium is zero, with the exception of an occasional Link Test Pulse 300. The Link Test Pulse, as defined in IEEE standard 802.3 Clause 14, signals that an active link connection exists. The Link Test Pulse is generally a 100 nanosecond positive pulse that repeats approximately every 16 milliseconds. Clause 28 Auto-Negotiation refers to the 10BASE-T Link Test Pulse as the Normal Link Pulse (NLP). Auto-Negotiation uses multiple Link Test Pulses to form a burst referred to as a Fast Link Pulse (FLP) Burst, as a signaling mechanism. Auto-Negotiation substitutes the FLP Burst in place of the single 10BASE-T Link Test Pulse. This approach increases the signaling capability of the link identifier, while maintaining backwards compatibility with 10BASE-T. The FLP Burst encodes the data (identifying modes of operation) transmitted by the Auto-Negotiation function.
100BASE-T Architecture and Nomenclature
With reference to FIG. 1, the 100BASE-T standard extends the IEEE standard 802.3 Media Access Control (MAC) sublayer 120 to 100 Mb/s and couples the MAC sublayer to a 100 Mb/s Physical Layer 101. The Physical Layer is comprised of additional sublayers including the Reconciliation Sublayer 103, Media Independent Interface (MII) Sublayer 130, Physical Coding Sublayer (PCS) 140, Physical Medium Attachment (PMA) sublayer 150, Physical Medium Dependent (PMD) sublayer 160 and, in a 100BASE-T4, 100BASE-T2 or 100BASE-TX environment, an optional Auto-Negotiation (AutoNeg) sublayer 170. The PMD sublayer 160 encompasses the Medium Dependent Interface (MDI) 180. The MDI provides the medium attachment, including the connector, to the medium 190, such as UTP or STP wiring.